Definition of roundel
1a small disk, especially a decorative medallion. a picture or pattern contained in a circle. Heraldry a plain filled circle as a charge (often with a special name according to color). British a circular identifying mark painted on military aircraft, as, for example, the red, white, and blue of the RAF. 2a short poem consisting of three stanzas of three lines each, rhyming alternately, with the opening words repeated as a refrain after the first and third stanzas. The form, a variant of the rondeau, was developed by Swinburne.